<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="../css/bootstrap.css">
    <script src="../js/bootstrap.js"></script>
    <style>
        .item1 div {
            border: 1px solid red;
        }

        .row {
            border: 1px solid blue;
        }
    </style>
</head>

<body>
    <div id="app" class="container">
        <div class="row item1">
            <!-- *-offset-n：表示向后移动n列 -->
            <div class="col-md-4 col-sm-4 col-xs-4">4列</div>
            <div class="col-md-2 col-md-offset-2 col-sm-2 col-xs-2">2列</div>
            <div class="col-md-3 col-md-offset-1 col-sm-3 col-xs-3">3列</div>
            <div class="col-md-3 col-sm-3 col-xs-3">3列</div>
        </div>
    </div>
</body>

</html>